Power supply circuit for antenna, antenna control system, and digital communication device

Abstract

A power supply circuit, an antenna control system, and a digital communication device are provided. The power supply circuit is adapted to supply electronic power to an antenna and includes a power management circuit and a pin. The power management circuit is coupled between a power input terminal and a power output terminal. In a first mode, the pin receives a mode control signal to control the power management circuit to deliver or not deliver electronic power of a power source from the power input terminal to the power output terminal. In a second mode, the pin stops receiving the mode control signal and provides a detection signal, which indicates whether the power supply circuit is overloaded. Thereby, power switching of the antenna and an overload detection/notification function are accomplished by using the single pin.

What is claimed is: 
     
       1. A power supply circuit, adapted to supply electric power to an antenna, the power supply circuit comprising:
 a power management circuit, coupled between a power input terminal and a power output terminal; and 
 a pin, coupled to the power management circuit, wherein 
 in a first mode, wherein the pin receives a mode control signal and provides the mode control signal to the power management circuit such that the power management circuit determines to deliver or not deliver electric power of a power source from the power input terminal to the power output terminal according to the mode control signal, and 
 in a second mode, the pin stops receiving the mode control signal and provides a detection signal indicating whether an overload occurs. 
 
     
     
       2. The power supply circuit according to  claim 1 , wherein in the second mode, when the overload does not occur, the power management circuit controls the pin through a positive feedback mechanism to maintain a trigger level of the mode control signal received in the first mode. 
     
     
       3. The power supply circuit according to  claim 1 , wherein in the second mode, when the overload occurs, the power management circuit stops supplying electric power of the power source to the power output terminal. 
     
     
       4. The power supply circuit according to  claim 1 , wherein the power management circuit comprises:
 a switch, coupled to the power output terminal; and 
 a positive feedback protection circuit, coupled among the pin, the switch, and the power input terminal, wherein 
 in the first mode, the positive feedback protection circuit turns the switch on or off according to a voltage level of the mode control signal received by the pin, and 
 in the second mode, the positive feedback protection circuit detects whether an overload occurs according to a current from the power source and changes a level of the detection signal when the overload occurs. 
 
     
     
       5. The power supply circuit according to  claim 4 , wherein in the second mode, when the overload does not occur, the positive feedback protection circuit controls the pin through a positive feedback mechanism to maintain a trigger level of the mode control signal received in the first mode. 
     
     
       6. The power supply circuit according to  claim 4 , wherein the positive feedback protection circuit comprises:
 a protection circuit, coupled between the power output tenninal and the switch; and 
 a positive feedback circuit, coupled among the protection circuit, the pin, and the switch, wherein 
 in the first mode, the positive feedback circuit turns the switch on or off according to the voltage level of the mode control signal received by the pin, and 
 in the second mode, the protection circuit detects whether the overload occurs according to the current and changes the level of the detection signal when the overload occurs. 
 
     
     
       7. The power supply circuit according to  claim 6 , wherein the positive feedback circuit comprises:
 an operational amplifier, having a positive input terminal coupled to the pin and the protection circuit, a negative input terminal coupled to a ground, and an output terminal coupled to the switch; and 
 a resistor, coupled between the positive input terminal and the output terminal of the operational amplifier. 
 
     
     
       8. The power supply circuit according to  claim 6 , wherein the protection circuit comprises:
 a first PNP bipolar junction transistor (BJT); 
 a first resistor; and 
 a second resistor; 
 wherein an emitter of the first PNP BJT is coupled to the power input terminal and a first end of the first resistor, a base of the first PNP BJT is coupled to a first end of the second resistor, a collector of the first PNP BJT is coupled to the switch, and a second end of the first resistor is coupled to the switch and a second end of the second resistor; 
 the positive feedback circuit comprises: 
 a second PNP BJT; 
 a third resistor; 
 a fourth resistor; 
 a fifth resistor; 
 a sixth resistor; and 
 an NPN BJT; 
 wherein an emitter of the second PNP BJT is coupled to a first end of the fourth resistor and the switch, a base of the second PNP BJT is coupled to a first end of the third resistor, and a collector of the second PNP BJT is coupled to the collector of the first PNP BJT, a first end of the fifth resistor, and the switch, 
 wherein a collector of the NPN BJT is coupled to a second end of the third resistor and a second end of the fourth resistor, a base of the NPN BJT is coupled to a second end of the sixth resistor, and an emitter of the NPN BJT is coupled to the ground, 
 wherein a second end of the fifth resistor and a first end of the sixth resistor are coupled to the pin. 
 
     
     
       9. The power supply circuit according to  claim 4 , wherein the positive feedback protection circuit comprises:
 a PNP BJT; 
 an NPN BJT; 
 a first resistor; 
 a second resistor; 
 a third resistor; 
 a fourth resistor; and 
 a fifth resistor, 
 wherein an emitter of the PNP BJT is coupled to the power input terminal and a first end of the first resistor, a base of the PNP BJT is coupled to a first end of the second resistor, and a collector of the PNP BJT is coupled to the switch and a first end of the fourth resistor, 
 wherein a collector of the NPN BJT is coupled to a second end of the second resistor and a second end of the third resistor, a base of the NPN BJT is coupled to a second end of the fifth resistor, and an emitter of the NPN BJT is coupled to a ground, 
 wherein a second end of the first resistor and a first end of the third resistor are coupled to the switch, and a second end of the fourth resistor and a first end of the fifth resistor are coupled to the pin. 
 
     
     
       10. The power supply circuit according to  claim 4 , wherein the positive feedback protection circuit comprises:
 a regulation circuit, configured to regulate a drop of a voltage received by the antenna when the overload occurs. 
 
     
     
       11. An antenna control system, comprising:
 the power supply circuit according to  claim 1 ; and 
 an antenna control circuit, configured to provide the mode control signal to the pin and receive the detection signal from the pin. 
 
     
     
       12. A digital communication device, comprising:
 the antenna control system according to  claim 11 ; 
 the power source, configured to supply electric power to the power input terminal of the power supply circuit; and 
 the antenna, configured to receive electric power from the power input terminal of the power supply circuit. 
 
     
     
       13. The digital communication device according to  claim 12 , being a set-top box or a digital TV. 
     
     
       14. A power supply circuit, comprising:
 a pin; 
 a positive feedback protection circuit, coupled to a power source; and 
 a switch, coupled between the positive feedback protection circuit and an antenna, wherein when the switch is turned on, electric power of the power source is supplied to the antenna through the positive feedback protection circuit and the switch, 
 wherein in a first mode, the positive feedback protection circuit maintains a trigger level of a mode control signal received by the pin and turns the switch on or off according to the trigger level, 
 wherein in a second mode, the positive feedback protection circuit detects a current from the power source, and when the current is overloaded, the positive feedback protection circuit turns off the switch and changes a level of the pin. 
 
     
     
       15. The power supply circuit according to  claim 14 , wherein the positive feedback protection circuit comprises:
 a PNP BJT; 
 an NPN BJT; 
 a first resistor; 
 a second resistor; 
 a third resistor; 
 a fourth resistor; and 
 a fifth resistor; 
 wherein an emitter of the PNP BJT is coupled to the power source and a first end of the first resistor, a base of the PNP BJT is coupled to a second end of the second resistor, and a collector of the PNP BJT is coupled to the switch and a first end of the fourth resistor, 
 wherein a collector of the NPN BJT is coupled to the second end of the second resistor and a second end of the third resistor, a base of the NPN BJT is coupled to a second end of the fifth resistor, and an emitter of the NPN BJT is coupled to a ground, 
 wherein a second end of the first resistor and a first end of the third resistor are coupled to the switch, a second end of the fourth resistor and a first end of the fifth resistor are coupled to the pin. 
 
     
     
       16. The power supply circuit according to  claim 14 , wherein the positive feedback protection circuit comprises:
 a protection circuit, coupled between the power source and the switch; and 
 a positive feedback circuit, coupled among the protection circuit, the pin, and the switch, wherein 
 in the first mode, the positive feedback circuit turns the switch on or off according to a voltage level of the mode control signal received by the pin, and 
 in the second mode, the protection circuit detects whether an overload occurs according to the current and changes a level of the detection signal when the overload occurs. 
 
     
     
       17. The power supply circuit according to  claim 16 , wherein the positive feedback circuit comprises:
 an operational amplifier, having a positive input terminal coupled to the pin and the protection circuit, a negative input terminal coupled to a ground, and an output terminal coupled to the switch; and 
 a resistor, coupled between the positive input terminal and the output terminal of the operational amplifier. 
 
     
     
       18. The power supply circuit according to  claim 16 , wherein the protection circuit comprises:
 a first PNP BJT; 
 a first resistor; and 
 a second resistor; 
 wherein an emitter of the first PNP BJT is coupled to the power source and a first end of the first resistor, a base of the first PNP BJT coupled to a first end of the second resistor, and a collector of the first PNP BJT is coupled to the switch, and a second end of the first resistor is coupled to the switch and a second end of the second resistor; 
 the positive feedback circuit comprises: 
 a second PNP BJT; 
 a third resistor; 
 a fourth resistor; 
 a fifth resistor; 
 a sixth resistor; and 
 an NPN BJT, 
 wherein an emitter of the second PNP BJT is coupled to a first end of the fourth resistor and the switch, a base of the second PNP BJT is coupled to a first end of the third resistor, and a collector of the second PNP BJT is coupled to the collector of the first PNP BJT, a first end of the fifth resistor, and the switch, 
 wherein a collector of the NPN BJT is coupled to a second end of the third resistor and a second end of the fourth resistor, a base of the NPN BJT is coupled to a second end of the sixth resistor, and an emitter of the NPN BJT is coupled to a ground, 
 wherein a second end of the fifth resistor and a first end of the sixth resistor are coupled to the pin. 
 
     
     
       19. The power supply circuit according to  claim 14 , wherein the positive feedback protection circuit comprises:
 a regulation circuit, configured to regulate a drop of a voltage received by the antenna when an overload occurs. 
 
     
     
       20. An antenna control system, comprising:
 the power supply circuit according to  claim 14 ; and 
 an antenna control circuit, configured to provide the mode control signal to the pin and receive the detection signal from the pin. 
 
     
     
       21. A digital communication device, comprising:
 the antenna control system according to  claim 20 ; 
 the power source; and 
 the antenna. 
 
     
     
       22. The digital communication device according to  claim 21 , wherein the digital communication device is a set-top box or a digital TV.